Cardiovascular diseases, respiratory diseases, and gastrointestinal diseases have been distinguished according to sounds auscultated from the body of a patient. Based upon measurements taken of the different sounds, medical practitioners have been able to diagnose diseases and proceed with treatments.
In order to make a precise diagnosis of an ailment based upon auscultated sounds, extensive empirical knowledge of various and diverse forms of auscultated sounds is necessary. Until recently, auscultation was more art than science since making a diagnosis was based mainly upon the trained ear of a caregiver and not based upon objectively measured data from recorded sounds.
With the advent of digital/electronic stethoscopes, auscultated sounds can be recorded in digital form, and computer programs manipulate the data to analyze characteristics of the recording. From this analysis, more precise diagnoses can be made based upon objective criteria and not just upon the trained ear of the attending caregiver.
It is well known to measure auscultated sounds from humans in order to make diagnoses of perceived pathology. However, auscultation for animals such as cattle is used infrequently. There have been very few efforts made to gather data from auscultated sounds for purposes of making conclusions as to the type of disease that may be occurring in a species of animal.
Particularly in a feed yard where it is necessary for cattle to be maintained at an optimum state of health for maximum weight gain to occur, it is critical that sick cattle be identified early for effective treatment and to contribute to biosecurity. The true state of health for cattle can be difficult to measure using traditional techniques such as observation of symptoms to include temperature, posture and visual signs (e.g. nasal discharge, depression, and abdominal fill.). In the example of the bovine species, case definitions for BRD traditionally include a minimally effective but objective rectal temperature and a subjective clinical score. Clinical trials indicate that objective lung scores provide stronger correlations than rectal temperatures to ultimate case fatality rates, retreatment rates, and therefore treatment costs. Cattle are visually evaluated when they first arrive at the feed yard, and the surge of adrenalin associated with handling, along with prey defensive mechanisms, can often mask disease symptoms. Stethoscopic evaluation of bovine heart and lung sounds can be used to evaluate the cardio-pulmonary efficiency or potential efficiency of cattle during various stages of arrival processing. However, because of the lack of current data in objectively categorizing animal heart and lung sounds, there is a need for developing an automated system and method that can assist a caregiver in assessing these sounds and making timely diagnoses.
Bovine respiratory disease is complex and is particularly difficult to accurately diagnose in the harsh environments where the animal's health assessment takes place; noisy with uncooperative patients at best requiring server restraint. The thick musculature that surrounds the thorax of cattle, the heavy hide and layers of fat renders the use of a stethoscope difficult to obtain sounds that can be interpreted for purposes of making an accurate diagnosis. Because of the difficulties encountered to effectively gather auscultated sounds from cattle, and a general lack of knowledge in the cattle industry as to how to interpret these sounds, the cattle industry has been slow in developing automated diagnostic processes that can effectively use data generated through auscultation.
Production animals are intentionally metabolically stressed to promote rapid weight gain in the feed yard. Nutrition technology and health management protocols strive to maximize daily weight gain, but weight gain itself can push the physiological limits of production animals beyond their ability to mount a compensatory response to; metabolic challenges, disease, weather environmental, and behavioral stresses. Determining the physiological capacity for stress of each production animal would allow for matching of the animal to an optimal production management strategy protocol. This optimization would enhance the production process causing a higher rate of return by minimizing valuable asset loss due to animal variations in abilities to handle physiological stress. If an animal's compensatory capabilities could be predicted prior to exposing the animal to the stresses inherent in production, then optimal production procedures could be implemented for each animal given its unique physiological profile and thus maximizing each animal's potential and minimizing each animals risks.
Cardiac performance/efficiency is measured by the cardiac output (CO) of an animal and is defined as heart rate (HR) multiplied by the stroke volume (SV) thus this relationship can be expressed as CO=(HR)(SV). The heart rate of an animal will typically increase at times of acute stress (both physical and psychological) due to increased automaticity (and therefore an increased rate) caused by catecholamine release during a sympathetic adrenergic response to stress. For production animals such as beef cattle, processing actions such as experienced in transporting the animals to and sorting the animals within a feed yard can be a series of very stressful events that predictably drive up the heart rates of the animals due to positive chronotropic effects of the sympathetic nervous system.
Respiratory performance/efficiency of an animal is the ability of the pulmonary system to adequately exchange gases allowing for metabolic variations while maintaining optimal functioning of vital organs. Part of the mechanism for handling the variations of metabolic changes is through perfusion matching with ventilation. Ventilation or respiratory drive, can in part be measured by respiratory rate.
When either the cardiac function or respiratory function is impaired, the other system may respond through compensatory mechanisms that attempt to maintain homeostasis for the animal. Maintaining homeostasis becomes more challenging if an animal is placed in stressful environments. Maintaining homeostasis under an impaired condition will consume organ system resources, and the animal may not be able to maintain homeostasis. The compromised state of an animal in this condition causes a reduction in the efficiencies of the animal's metabolic system, which in turn manifest in consequences such as a decreased daily weight gain or observable increases in morbidity.
Therefore, in the case of the bovine, in addition to an acute lung score for lung pathology detection, there is a need to determine which production animals may be prone to not tolerating metabolic stress or may be inefficient in adapting to metabolic stresses that could result in poor performance over time. The poor performance can range from inadequate weight gain to acute morbidity and/or mortality.
While there may be some known methods and systems that account for cardiac performance in determining the health status of animals, there is a further need to provide new ways of determining when animals that are not capable of tolerating metabolic stress so that very early predictions can be made about the performance potential of an animals.